Panel heat exchangers formed from thermoplastic polymers and methods for the manufacture of such heat exchangers are known. For instance, a number of heat exchangers formed from thermoplastic polymers and methods for the manufacture thereof are disclosed in PCT Patent Application WO91/02209 of A. J. Cesaroni, published Feb. 21, 1991, and in the published patent applications referred to therein. Thermoplastic polymer heat exchangers of a tubular construction are described in U.S. Pat. Nos. 4,923,004, and 5,078,946, issued May 8, 1990 and Jan. 7, 1992, respectively, both of E. L. Fletcher and T. H. Kho, in which tubes are integrally formed with a manifold section in a moulding or similar process. A preferred material of construction for the heat exchangers is polyamide, especially aliphatic polyamide.
While heat exchangers formed from thermoplastic polymers have been fabricated by the techniques described in the above patents and published patent applications, improvement in the construction and methods of fabrication would be beneficial to add further flexibility and economy to the fabrication and use of heat exchangers formed from thermoplastic polymers. In particular, assembly of tubes into headers or manifolds or other structures in the manufacture of tube heat exchangers is usually a tedious and time-consuming process, often involving use of adhesives to bond the tubes into position.
British Patent 1,379,511--Gibbons et al, published 1975, discloses a method of making a heat exchanger in which a low-melting metal is first poured into a cavity surrounding tubes, preferably incorporating plug portions protruding into the tubes to keep the tubes open; then polypropylene (PP) is cast on the ends to form headers encapsulating the tubes. Finally the low-melting metal is melted out, leaving the PP exposed to the inside of the heat exchanger.
U.S. Pat. No. 2,225,856--Buck (1940) discloses a heat exchanger with aluminum tubes sealed through an apertured sheet or plate of resilient rubber between pairs of spaced header plates. There is no suggestion to cast a polymer instead of using a preformed apertured sheet of rubber.
U.S. Pat. No. 4,323,115--Stafford et al (1982) discloses a tube heat exchanger with tube sheets comprising first a layer of insulation such as fiberglass reinforced polymethyl methacrylate, then with preferably a liquid resin poured in around the tubes on top of the insulation. Preferably catalysed epoxy resin are used which set at ambient temperatures. A key goal is to use a resin that can be burned out without damaging the tubes which can be made of plastic. Instead of the insulation material, a temporary wooden form can be used to hold in place the liquid resin until it solidifies. As an option, the epoxy can be in two layers with fibers in one for insulation and particles in the other for reinforced strength. In any event, there is no suggestion of injecting a thermo plastic filler between two solid plates to form a header, with tubes threaded through holes in the two solid plates.